Trigger fuse switch assembly

ABSTRACT

A trigger fuse switch assembly wherein a trigger fuse may only be inserted into the assembly in its correct operative position being held in place by a spring terminal. When the fuse is tripped, the striker pin thereof engages a pushrod of the assembly to cause a movable contact to either make or break a circuit therebetween. The stationary contacts may be selectively placed to provide normally open or closed operation of the switch assembly.

D United States Patent ml 3,593,247

[72] Inven Jam" D- (Yollins; 2,965,873 12/1960 Sindelar. 337/195 X RalphD. lrnmel, both 01 Bultalo, NY. 2,882,369 4/1959 Bauer 1, 337/ 198 X1211 Appl. No 819,020 2.581.308 1/1952 Smith 337/186 X 1221 Filc p 21969 2,405,929 8/1946 Wald 337/147 X 1451 Patented J ".1 2,306,15312/1942 Biermanns et al. N 337/142 X 1 1 Assignee wrstinshwsl ElectricCorporation |,054,7|1 3/1913 Schramm 337/208 x FOREIGN PATENTS 791,58412/1935 France 337/225 16 4 7 .4 337 148 541 TRIGGER ruse SWITCHASSEMBLY 9/195 Germany I 1 Claim, 6 Drawing Figs. PrimaryExaminer-Bernard A. Gilheany Assistant Examiner-Dewitt M. MorganAttorneys-1 H. Henson,C. F. Ron: and A. S. Oddi [SI] ..ll0lh85/S0 i 1sum. 377/5 ABS'IRAC'I': A trigger fuse switch assembly wherein a trigger143,145, I47, I48, 186, I87, 190, 194, 195, 193, fuse may only beinserted into the assembly in its correct HQ 244 operative positionbeing held in place by a spring terminal. When the fuse is tripped, thestriker pin thereof engages a [56] Rehnnm cued pushrod of the assemblyto cause a movable contact to either UNITED STATES PATENTS make or breaka circuit therebetween. The stationary contacts 3,274,358 9/1966Hallerberg 337/148 may be selectively placed to provide normally open orclosed 3,263,048 7/1966 Hicks 337/142 X operation of the switchassembly.

TRIGGER FUSE SWITCH ASSEMBLY BACKGROUND OF THE INVENTION l. Field of theInvention The present invention relates to switch assemblies and, moreparticularly, to switch assemblies adapted to be operative with triggerfuses.

2. Discussion of the Prior Art Trigger fuses are commonly utilized tomonitor the condition of main power fuses which are connected in serieswith semiconductor power devices utilized in high-power rectifierequipment. In such high-power conversion equipment employingsemiconductor diodes or thyristors, 400 to 500 power fuses may beutilized in conjunction with the semiconductor devices. If asemiconductor device should fail by shorting, the power fuse will blowopen that particular circuit. The blowing of the power fuse appliesvoltage to a trigger fuse which is connected in parallel with the powerfuse causing the trigger fuse to blow and mechanically operate a pair ofcontacts to activate a circuit which will be indicative of the specificlocation of the semiconductor device failure and the main power fusethat has blown. In typical application the trigger fuse when activatedwill cause an indicator light to be turned on or off or to cause anaudible-signal-generating device to be energized.

A commonly used method of mounting the trigger fuse is to place the fusebetween a pair of fuse clips which are mounted on an insulator board. Amicroswitch is mounted on the insu lator board adjacent the striker inend of the trigger fuse so that when the trigger fuse is blown thecontacts of the microswitch will either opened or closed to activate anindica tor circuit. The use of such a trigger fuse mounting has a numberof serious disadvantages. The use of a microswitch is expensive, andcare must be taken to accurately place the fuse between the fuse clipsto insure that the striker pin end of the trigger fuse is disposed inposition to activate the microswitch when the fuse is blown. Also caremust be taken to insure that the trigger fuse is not placed into thefuse clips backwards since no inherent protection is provided againstsuch a possibilityv Additionally, when a large number of trigger fusesare to be utilized for monitoring main power fuses, the use of fuseclips and microswitches requires a large amount of space as well aspresenting difficult wiring problems due to the large number ofmicroswitches required. Moreover, the microswitches utilized may not bereadily adaptable to either normally open or normally closed operationwhich may be highly desirable in certain applications.

It would therefore be highly desirable ifa trigger fuse switch assemblycould be provided which is of low cost, requires small physical spacefor mounting, permits mounting of a large number in a minimum amount ofspace, requires that the trigger fuse be inserted into the assembly inthe correct position, insures that the striker pin end of the triggerfuse is disposed in position to activate contacts of the switch assemblyand permits easy modification of the assembly for normally open ornormally closed operation ofthe switch.

SUMMARY OFTHE INVENTION Broadly the present invention provides a triggerfuse switch assembly wherein the trigger fuse may only be properlyinserted to the assembly and is held to insure operation of the contactsthereof when activated, with the assembly being readily adaptable foreither normally open or normally closed operation.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a pictorial diagram of thefuse assembly of the present assembly in its normally open position;

FIG. 2 is a side view of the fuse assembly having a partially cut awayportion; I

FIG. 3 is a partial top view showing the fuse mourning;

FIG. 4 is a bottom sectional view taken along the line IV-IV of FIG. 2with the trigger fuse blown;

FIG. 5 is a bottom view taken along the line IV-IV of FIG. 2 with thetrigger fuse in its unblown condition; and

FIG. 6 is a partial side view of the contact portion of the assembly inits normally closed position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, theswitch assembly includes a base member [0 which may be formed by moldingfrom a high-strength molded glass polyester insulating material forexample. A trigger fuse I2 is shown inserted in the assembly andcomprises a long ferrule 14, a short ferrule I6, and a tubu lar portionI8 therebetween. The outer end of the long ferrule 14 defines thestriker pin end 20 of the fuse and the outer end of the short ferrule I6defines the base end 22 of the fuse I2. When the fuse I2 blows, astriker pin 24 (see FIG. 4) is ejected from the striker pin end 20 ofthe trigger fuse 12. In the normal unblown condition of the fuse I2, thestriker pin 24 is recessed within the long ferrule I4 as shown in FIG.5.

The fuse I2 is held in place by a spring clip terminal 26 and a fuseterminal 28. The spring clip terminal 26 may, for example, be made ofberyllium copper, which provides a good electrical connection to theshort ferrule 16. The spring clip 26 is mounted in a slot 27 of the basemember 10. The spring clip 26 has a top portion 30 which extends abovethe base I0 so that it may be moved away from the short ferrule I6 topermit the insertion or removal of the fuse I2. The spring slip 26 has aU-shaped portion 32 which extends downwardly into the slot 27. A flatportion 34 of the spring clip 26 has a hole disposed therein which restsover a shoulder portion 36 of the base 10 so that the spring clip 26 maybe securely mounted to the base I0 via a screw 38. Adjacent the flatportion 34 of the spring clip 26 is a portion 40 which rests on aninside surface 42 of the base I0. A hole is provided in the portion 40through which a terminal screw 44 is inserted and secured into the baseI0. A contact washer 46 is placed between the head of the terminal screw44 and the portion 40 of the spring clip 26. The contact washer 46 hastwo concave portions thereon adapted to receive up to two roundelectrical conductors so as to insure good electrical and mechanicalconnection thereto. The terminal screw 44 thus serves as one terminalpoint, for example, for connection to a main power fuse of semiconductorpower equipment.

The spring clip 26 also includes a projection 48 thereon disposeddirectly behind the base end 22 of the fuse I2 which abuts there underthe tension of the spring clip 26 to force the striker pin end 20 of thefuse 12 against the fuse terminal 28. The use of the spring clipterminal 26 thus provides good electrical contact to the short ferrule16 of the fuse and moreover insures that the striker pin end 20 of thefuse 12 is held under tension against the fuse terminal 28. Thisarrangement adequately takes care of the relatively large variation intrigger fuse length.

The fuse terminal 28 is generally L-shaped and includes a bottom portion50 which has a hole therein through which a mounting screw 52 isextended into the base I0 to secure the fuse terminal 28 thereto. Thefuse terminal 28 also includes a fuse-receiving portion 53 having a slot54 therein through which the striker pin 24 of the fuse 12 may extendwhen the fuse I2 is blown. The portion 53 also includes a pair of wingportions 56 which prevent the fuse 12 from flipping out of the assemblyor working its way out under the force of the spring clip terminal 26. Asecond terminal screw 58 is provided which extends through the portion50 of the fuse terminal 28 into the base I0. A contact washer 60 similarto the contact 46 is provided between the head of the screw 58 and theportion 50 and is adapted to receive electrical wire for connection, forexample, to the other side ofa main power fuse so that the terminalscrews 44 and 58 are connected in parallel across a main power fuse. Ashoulder portion 62 is provided in the base 10 which has a semicirculartop Indentation 64 thereof which serves to seat the fuse I2 at the largeferrule I4 diameter. An aperture 66 is provided through the base 10 fromthe inner surface 42 to the bottom surface 68 of the base III. Thisaperture may be utilized for mounting the assembly to any suitablesurface from either end of the aperture 66 with any suitable form ofsecuring device. A mounting lug 70 is provided on the bottom surface 68so as to aid in seating the assembly on a mounting surface and is usefulwhen a plurality of assemblies are mounted side by side.

FIG. 3 demonstrates the feature that the fuse 14 cannot be mounted inthe assembly in the backwards position. For proper mounting of the fuse12 between the terminals 26 and 28, it is necessary that the longferrule I4 abut against the fuse terminal 28 so that the striker pin 24thereof will be in the proper position. FIG. 3 shows the diameter of thelong ferrule I4 to be DI. The diameter of the short ferrule I6 may alsobe D] or may vary from this value slightly. However the diameter of thetubular insulating portion I8 between the ferrules I4 and 16 is of asmaller diameter D2. As shown in FIG. 3 the base 10 is designed to havestop portions 72 which extends into the slot 27 so as to define thedistance D2 thcrebetween. The distance D2 is smaller than the distanceDI, but it is of sufficient width to permit the passage ofthe tubularportion 18 of the fuse I2 therethroughv The short ferrule I6 fits withinthe slot 28 with the tubular portion I8 fitting between the stopportions 72 when the fuse I2 is in its normal operating position betweenthe terminals 26 and 28. If it were attempted to reverse the fuse sothat the long ferrule portion 14 were to be inserted to contact thespring clip terminal 26, this would not be possible since the longferrule I4 would have to extend through the stop portions 72 which istoo small of a gap D2 therebetween to permit the passage of the largerdiameter DI of the long ferrule I4. Thus the fuse I2 could not beinserted backwards into the fuse assembly of the present invention andmust be disposed between the contacts 26 and 28 so that the long ferruleabuts against the fuse terminal 28 and the striker pin 24 is disposed inposition to be ejected when the fuse is tripped.

Referring now to FIGS. 4 and 5, along with FIG. 2, a pushrod 74 having alarge-diameter section 75 is disposed in a passageway 76 in the baseIII. The passageway 76 extends laterally from behind the slot 54 of thefuse terminal 28 to a rest portion 78 of the base 10. The pushrod 74may, for example, comprise a plastic insulating material and may ideallybe made of a different color than the base 10. An opening 79 is providedin the base It) behind the fuse terminal 28 so that an observer may viewthe osition of the pushrod 74 to determine visually whether the triggerfuse I2 has been blown or not. The pushrod 74 has a small-diameterportion 80 which extends through a contact opening 82 in the base I intoa passageway 84 in the base I0 which is of a smaller diameter than thepassageway 76 however on the same axis.

A movable contact 86 which may comprise a suitable electricallyconductive material, such as, brass or beryllium copper coated withsilver, and which may have a substantially rectangular shape is providedwith a hole therein of sufficient diameter to just fit over thesmall-diameter portion 80 of the pushrod 74. As shown in FIGS. 2 andwhen the fuse I2 is in its unblown state the movable contact 86 abutsagainst the end of the larger diameter section 75 of the pushrod 74 andagainst the rest portion 78 of the base I0. A coil spring 88 is disposedaround the small section 80 of the pushrod 74 and is disposed betweenthe movable contact 86 and a shoulder 90 at the inside edge of thepassageway 84. The coil spring 88 thus holds the movable contact 86under spring tension against the rest portion 78 when the fuse I2 is inits unblown condition as shown in FIGS. 2 and 5.

As better shown in FIG. 4, when the fuse I2 is blown, the striker pin 24is extended and passes through the slot 54 of the fuse terminal 28 tostrike the outer end of the pushrod section 74 causing it to be moved tothe right in the passageway 76. The movable contact 86 abutting againstthe opposite end of the large-diameter section 75 of the pushrod 74 istherefore moved away from the surface 78 of the base 10. The spring 88is compressed as the contact 86 moves to the right. The small section ofthe pushrod 74 extends further to the right into the passageway 84. Themovable contact 86 moves to the right against the pressure of the coilspring 88 until the movable contact 86 abuts against a pair of fixedcontacts 92 and 94. The fixed contacts 92 and 94 are made from asuitable electrically conductive material such as brass or berylliumcopper coated with silver, for example. The contact between the movablecontact 86 and the fixed contacts 92 and 94 occurs at contact points 96and 98 of the fixed terminals 92 and 94, respectively, with the points96 and 98 having sharp points to insure good electrical contact betweenthe fixed contacts 92 and 94 and the movable contact 86. Both themovable contact 86 and the fixed contacts 92 and 94 are desirablyprovided with a relatively heavy silver plating to insure goodelectrical conductivity.

The base I0 is provided with four contact terminal positions I, 2, 3 and4. As shown in FIGS. 1 and 2, when the switch assembly is in itsnormally open state, the fixed contact 92 is disposed in the terminalposition 3 and the fixed contact 94 is disposed in the terminal position2. The fixed contact 92 is secured in the terminal position 2 by aterminal screw 100 which extends through a hole in the fixed contact 92into the base I0 in a slot I02 which defines the terminal position 2. Acontact washer I04 is situated between the head of the terminal screwI00 and the fixed contact 92 similar to the contacts 46 and 60 and isadapted to receive up to two round wire conductors. A terminal screw I06secures the fixed contact 94 in the terminal position 3 defined by aslot 107, with the screw I06 passing through a contact washer I08similar to the contact 104 and the terminal 94 into the base 10. Thefixed contacts 92 and 94 have bottom lug portions I10 and 112 which arebent inwardly with respect to sidewalls of the base [0 so that theseportions of the fixed contacts 92 and 94 are projecting over the base 10adjacent the contact opening 82 of the base It]. The fixed contact 92has another contact point "4 opposite the contact point 96 and the fixedcontact 94 has a contact point I I6 opposite the contact point 98. Thecontacts points I14 and I16 serve no purpose when the switch assembly isoperative in its normally open state, but come into operation when theswitch assembly is changed to its normally closed state of operation.

An additional terminal screw I20 is provided in the screw terminalposition 4 and serves to secure a fixed terminal 122 which may comprisea sliver-coated electrically conductive member to the base 10. Thecontact I22 has a substantially U- shape and is secured by the screwwhich is passed through a contact washer I24 and the fixed terminal I22into the base I0. The terminal screw I20 in the terminal position 4 isprovided to supply an ideal output terminal for the connection of anindicating light such as a neon bulb or other indicator light to theswitch assembly.

FIG. 6 shows how the switch assembly of the present invention can bereadily converted from a normally open type of switch to a normallyclosed type of switch. The conversion from the normally open type ofswitch is shown in FIGS. 1 and 2 to the normally closed type of switchof FIG. 6 may be accomplished in the following fashion. The fixedcontacts 92 and 94 are removed from the terminal positions 3 and 2,respectively. The fixed contact 92 is then inserted into the terminal 2position on the same side of the base 10 as it was previously disposed.The fixed contact 94 is disposed in the terminal I position being fixedtherein by the terminal screw I06 which previously held this contact inthe terminal 2 position. The contact 94 is also disposed on the sameside of the base I0 in FIG. 6 as it was in the embodiments of FIGS. 1and 2.

As can be seen in FIG. 6 the contact point II4 of the contact 92directly contacts the movable contact 86 with the coil spring 88insuring good electrical and mechanical contact therebetween. 0n theother side of the base I0, in the embodi ment of FIG. 6, the contactpoint 116 would also contact the movable contact 86. Thus the switchassembly as shown in FIG. 6 provides a normally closed type of switchassembly and only requires the movement of the two fixed contacts 92 and94 to effect this modification.

ln the embodiment of FIG. 6, when the trigger fuse I2 is tripped, thestriker pin 24 thereof forces the pushrod 74 against the movable contact86 thereby driving the movable contact 86 away from the fixed contacts92 and 94 opening the closed contacts therethrough. The opening of thesecontacts is thus indicative that the trigger fuse 12 has been blown.

Although the present invention has been described with a certain degreeof particularity. it should be understood that the present disclosurehas been made only by way of example and that numerous changes in thedetails of construction and the combination and arrangement of parts andelements can be resorted to without departing from the spirit and thescope of the present invention.

We claim as our invention:

l. A switch asembly operative with a trigger fuse operative to eject astriker pin when blown from one end thereof comprising:

a base member comprising an insulating material:

a fuse terminal mounted on said base member for receiving said one endof said fuse;

a spring terminal mounted on said base member for receiving the otherend of said fuse and forcing said one end into contact with said fuseterminal;

a pair of fixed contacts mounted on said base member;

a movable contact;

activating means disposed between said one end of said trigger fuse andsaid movable contact to move said movable contact with respect to saidfixed contacts to either open or close a circuit therebetwcen when saidfuse is blown,

said activation means including a pushrod disposed within said basemember between said fuse terminal and said movable contact, and biasingmeans for said movable contact to bias said movable contact to a restposition when said fuse is in its unblown state,

said fuse terminal having an aperture therein permitting said strikerpin to pass therethrough when ejected to engage said pushrod and movesaid movable contact,

said base member including a stop portion thereon preventing said fusefrom being disposed between said fuse terminal and said spring terminalexcept with said one end adjacent said fuse terminal,

said base member also including a plurality of terminal positions forsaid fixed contacts,

when said pair of fixed contacts are disposed in a first set of saidplurality of terminal positions, said assembly being operative as anormally open switch with said movable contact biased away from saidfixed contacts by said biasing means,

when said pair of fixed contacts are disposed in a second set of saidplurality of terminal positions, said assembly being operative as anormally closed switch with said movable contact being biased againstsaid fixed contacts by said biasing means; and

an auxiliary fixed terminal disposed in one of said plurality ofterminal positions for providing an auxiliary electrical connection tosaid assembly,

said pair of fixed contacts each including a pair of contact points onopposite sides thereof,

when said pair of fixed contacts are disposed in said first set ofterminal positions, said contact points on one side of each of said pairof fixed contacts making contact with said movable contact when saidfuse is blown,

when said pair of fixed contacts are disposed in said second set ofterminal positions, said contact points on the other side of each ofsaid pair of fixed contacts making contact with said movable contactwhen said fuse in unblown.

1. A switch assembly operative with a trigger fuse operative to eject astriker pin when blown from one end thereof comprising: a base membercomprising an insulating material: a fuse terminal mounted on said basemember for receiving said one end of said fuse; a spring terminalmounted on said base member for receiving the other end of said fuse andforcing said one end into contact with said fuse terminal; a pair offixed contacts mounted on said base member; a movable contact;activating means disposed between said one end of said trigger fuse andsaid movable contact to move said movable contact with respect to saidfixed contacts to either open or close a circuit therebetween when saidfuse is blown, said activation means including a pushrod disposed withinsaid base member between said fuse terminal and said movable contact,and biasing means for said movable contact to bias said movable contactto a rest position when said fuse is in its unblown state, said fuseterminal having an aperture therein permiTting said striker pin to passtherethrough when ejected to engage said pushrod and move said movablecontact, said base member including a stop portion thereon preventingsaid fuse from being disposed between said fuse terminal and said springterminal except with said one end adjacent said fuse terminal, said basemember also including a plurality of terminal positions for said fixedcontacts, when said pair of fixed contacts are disposed in a first setof said plurality of terminal positions, said assembly being operativeas a normally open switch with said movable contact biased away fromsaid fixed contacts by said biasing means, when said pair of fixedcontacts are disposed in a second set of said plurality of terminalpositions, said assembly being operative as a normally closed switchwith said movable contact being biased against said fixed contacts bysaid biasing means; and an auxiliary fixed terminal disposed in one ofsaid plurality of terminal positions for providing an auxiliaryelectrical connection to said assembly, said pair of fixed contacts eachincluding a pair of contact points on opposite sides thereof, when saidpair of fixed contacts are disposed in said first set of terminalpositions, said contact points on one side of each of said pair of fixedcontacts making contact with said movable contact when said fuse isblown, when said pair of fixed contacts are disposed in said second setof terminal positions, said contact points on the other side of each ofsaid pair of fixed contacts making contact with said movable contactwhen said fuse in unblown.